1. The Field of the Invention
The present invention relates generally engines, and more particularly, but not necessarily entirely, to internal combustion engines having pistons with a variable stroke length.
2. Description of Related Art
Internal combustion engines with reciprocating pistons are commonly used for powering automobiles. A break-away side view of a prior art engine, indicated generally at 1, is shown in FIG. 22. As is known in the art of internal combustion engines, pistons 2 are received in cylinders 3 and are caused to reciprocate in a direction parallel with the cylinders 3 along the movement axis 4 upon the combustion of fuel within the cylinders 3. Connecting rods 5 are attached to the pistons 2 and to a crankshaft 6. The movement of the pistons 2 is transferred to the crankshaft 6 through the connecting rods 5. The crankshaft 6 customarily extends in a direction along a rotation axis 7 that is perpendicular to the piston movement axis 4. Moreover, as the pistons 2 move along the movement axis 4, the connecting rods 5 move a fixed radial distance 8 from the axis of rotation 7 of the crankshaft 6.
The pistons 2 have a stroke length correlated with the radial distance 8. The stroke length extends between a top dead center position, or the position at which a piston reaches the top of its travel, to the bottom dead center position, or the extreme bottom of the piston stroke. Internal combustion engines are commonly designed with a fixed stroke length and may be configured to provide maximum operating efficiency at a given throttle position. Accordingly, when the engine is not operating at that given throttle position, the engine will be less efficient, resulting in wastage of fuel or diminished power output, for example.
Moreover, the range of output capabilities is fixed in the prior art engine so that the engine may not be well suited for variable operational needs. For example, engines are commonly built with a specific purpose in mind. Some engines are built to produce economical transportation. These engines are commonly associated with low power capabilities. Other engines may be manufactured to produce high performance and high speeds. These engines are commonly associated with low fuel mileage. Other engines are produced with high towing power in mind. These engines may not be suitable for high speed functions or high fuel economy. Accordingly, the prior art engines have experienced a compromise between such operational features as economy and power.
It is known in the art to vary the stroke length of the piston to modify the operating characteristics of the internal combustion engine. For example, U.S. Pat. No. 5,927,236 (granted Jul. 27, 1999 to Gonzalez) discloses a variable stroke mechanism for internal combustion engines utilizing gear sets to modify the length of the connecting rod. The mechanism is designed to increase the efficiency of the engine by imposing a larger expansion stroke and a shorter intake stroke. However, the gear sets increase the complexity and cost of the engine, and make operation and repair more difficult.
Also, U.S. Pat. No. 5,136,987 (granted Aug. 11, 1992 to Schechter et al.) discloses a variable displacement and compression ratio piston engine. A connecting rod is attached to the piston and a swing plate. The swing plate is pivotally fixed to the engine block at one end and is placed between the connection rod and a crankshaft. A hydraulically controlled adjustment link is pivotally fixed to the engine block at one end and to the connecting rod and the swing plate at the other end. The connecting rod and crankshaft are attached to the swing plate through slots in the swing plate such that the hydraulically controlled adjustment link can vary the distance between the piston and the crankshaft to thereby vary the stroke length. However, the sliding action of the connecting rod and the crankshaft in the slots in the swing plate may cause undue friction and wear in the engine.
The prior art is thus characterized by several disadvantages that are addressed by the present invention. The present invention minimizes, and in some aspects eliminates, the above-mentioned failures, and other problems, by utilizing the methods and structural features described herein.
It would therefore be an advancement in the prior art to provide an engine that allows for adjustment of the operational characteristics of the engine in a simple manner, so that the engine is not required to compromise between power and economy. It would also be an improvement in the prior art to provide such an engine that allows for adjustment of the radial distances between the connecting rod and the axis of rotation of the crankshaft to thereby provide a variable stroke length of the piston. It would be a further advancement in the art to provide such an engine that provides for adjustment of the piston stroke length by allowing the axis of rotation of the crankshaft to extend at a non-perpendicular angle with respect to the movement axis of the piston. It would be an additional advancement over the prior art variable-stroke engine crankshafts, which typically include moving parts, to provide a variable-stroke engine having a solid crankshaft with no moving parts, which would be less prone to failure or to require excessive maintenance.
The features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by the practice of the invention without undue experimentation. The features and advantages of the invention may be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims.